This invention relates to a cleaning system of a printing press and more particularly to a combination of an impression cylinder and a cleaning unit therefor of an offset sheet-fed press.
An offset printing press of general type comprises in combination of a plate cylinder, a blanket cylinder, an impression cylinder and intermediate cylinder which are arranged to be mutually rotatable in contacting conditions, a printed paper recovery unit, an inking unit, a cleaning unit and the like.
With the offset printing press of the character described above, in an actual printing operation, printing liquid such as ink is transferred on an outer peripheral surface of the respective cylinders, for example, impression cylinder through the blanket cylinder, and dirt or paper dust or the like will be adversely stuck thereon during the printing operation. The dirt or dust thus stuck on the impression cylinder surface will form protrusions thereon which obstruct precise printing operation and make it impossible to obtain clearly printed materials.
Under these circumstances, several kinds of cleaning devices for cleaning the respective cylinders, for example, for the blanket cylinder has been developed, and a typical type of these cleaning devices or units comprises a magazine roll around which a cleaning cloth or the like is wound, a used cleaning cloth take-up roll, a cleaning liquid supply means for applying the cleaning liquid to the cleaning cloth, and a pressing member such as pneumatic pad for pressing the cleaning cloth against the outer peripheral surface of the cylinder. In the actual cleaning, the cylinder is rotated and the cleaning cloth is stepwisely drawn out under the pressed condition against the cylinder by suitable means.
The cleaning operation involves the following disadvantages or drawbacks.
(a) The draw-out of the cleaning cloth under the pressed condition requires much force for drawing out the same and it is also required for the cleaning cloth to apply a considerably large tension. This requires some strengthening means for a drive system and hence the whole structure of the press to impart the stiffness thereto, which results in enlargement and heavy weight of the whole structure of the press, thus being complicated and noneconomical.
(b) In a case where it is required to remove the cleaning cloth from the impression cylinder, the cleaning cloth pressing means has to be everytime moved in a direction apart from the cylinder, so that the pressing means and hence the press itself will be complicated.
In another aspect, however, regarding the cleaning of the impression cylinder which are generally provided with hook-shaped grippers for gripping a paper sheet in a condition of projecting outwardly from the outer peripheral surface of the impression cylinder, the location of these grippers may provide the following defects or drawbacks in the cleaning operation.
(c) Because of the projection of the grippers, it is considerably difficult to clean the area of the impression cylinder near the projecting grippers.
(d) The projecting grippers may damage the cleaning cloth during the rotation thereof under the pressed condition by means of such as pressing pad.
(e) The grippers may themselves be damaged during the rotation of the impression cylinder, which results in the damage of the offset press.
Taking the above-mentioned defects or drawbacks into consideration, the cleaning of the respective cylinders, particularly impression cylinder, is often carried out manually. Such manual cleaning working is however undertaken in a narrow space between the respective cylinders and various printing units under the rotating condition of the cylinders, thus being dangerous and a desirable cleaning effect was not expected. These drawbacks require as a consequence long cleaning time and result in the reduction of the production efficiency of the offset printing press.